Current wireless communication standards support Internet Protocol Multimedia Domain (IPMMD) that converges IP and telecom services. The wireless IPMMD has opened up a whole new market segment for wireless network operators and service providers. The IPMMD provides a control environment to a wireless network operator to offer countless enriched Internet services to its customers, thereby allowing the operator to break into a fast-growing market segment and increasing operation revenues.
In order for a wireless user to receive these IPMMD services, the user has to register in the IPMMD registrar serving call state control function (S-CSCF) that is a SIP proxy server. According to current standards, a home interrogating CSCF (I-CSCF), which is another SIP proxy server, has to allocate an S-CSCF in the home network domain as a registrar for that user to register and receive IPMMD services.
Conventional methods for assigning a user to an S-CSCF for registration include random selection and round robin. With random selection, the I-CSCF simply randomly assigns users to an S-CSCF. With round robin, the I-CSCF assigns users to an S-CSCF based on the number of other users assigned. Thus, for example, for a system having only two S-CSCFs, the I-CSCF may assign a first user to the first S-CSCF, a second user to the second S-CSCF, a third user to the first S-CSCF, and so on. However, even if the I-CSCF keeps track of how many users are assigned to each S-CSCF at any one time, neither this method nor the random selection method are able to provide a balanced load for the system based on the actual loads of the S-CSCFs in the system. The S-CSCFs are assigned either randomly or simply based on the number of registered users.